1. Field of the Invention
The present invention relates to a position detection apparatus, and more specifically relates to a photoelectric encoder.
2. Description of Related Art
Photoelectric encoders have been widely used as a precision length-measuring device or a precision position detector (for example, JP 5553669 B).
A photoelectric encoder includes a scale and a detection head part provided to be relatively movable along the scale in a length measurement direction.
A bright/dark pattern is provided on the scale. FIG. 1 illustrates a scale 20. As illustrated in FIG. 1, a scale pattern is formed by arranging a predetermined patterned chromium film 22 on a glass substrate 21.
The photoelectric encoder has two types of a reflective type and a transmissive type.
In a reflective photoelectric encoder, a light source and a light receiving part are provided on the same side of a scale, and the light receiving part receives a bright/dark pattern of light reflected by the scale. In a transmissive photoelectric encoder, a light source and a light receiving part are provided on each side of a scale, and the light receiving part receives a bright/dark pattern of light transmitted through the scale.
The layout of the constituent elements in the reflective photoelectric encoder is different from that in the transmissive photoelectric encoder, and which causes difference in external size or shape of a product. The reflective photoelectric encoder or the transmissive photoelectric encoder is appropriately selected according to usage or an installation space of the photoelectric encoder.